A radio-telescope system that is sensitive to Fourier components on a series of equally spaced concentric ellipses in the (u, v)-plane has a principal response pattern composed of a main beam and a series of ringlobes. This situation arises in east-west aperture-synthesis systems depending on Earth rotation. A method has been discovered of separating the response pattern into terms representing such a beam and a series of ringlobes. Unlike the grating sidelobes of more familiar radio-telescope arrays, the ringlobes are strongly asymmetrical; when they scan a source, they not only filter out the high spatial frequencies but also take the half-order derivative. However, all the ringlobes have essentially the same profile, merely diminishing in amplitude in inverse proportion to the square root of the order. In addition, each ringlobe possesses a negative skirt on the interior side. Thus a strong interfering source in a ringlobe may produce hitherto undescribed effects in the field of view of the main beam. The paper considers briefly arrays that are not in an east-west line and introduces approaches and concepts, such as principal transfer function, that may be of more general application. Subject headings: instruments - radio radiation
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Bracewell et al. (1973) studied this question.